Spring supported dual element face seal with a run surface sleeve

ABSTRACT

The invention provides a seal for a rotatable shaft. The seal includes an inner case mountable to the shaft and having a body and first and second flanges extending radially outward from the body. The seal includes first and second sealing discs operable to seal against the first and second flanges of the inner case. The sealing discs are immovably associated with a housing spaced from the shaft. A spring encircles the shaft and inner case to urge the sealing discs against the flanges. The spring rate of the spring is controlled to enhance sealing, reduce turning torque, and extend life of the seal.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/540,468 for a SPRING SUPPORTED DUAL ELEMENT FACESEAL WITH A RUN SURFACE SLEEVE, filed on Jan. 30, 2004, which is herebyincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Technical Field

The invention relates to a seal disposed between two relatively moveableparts wherein the seal has a relatively moveable relationship to atleast one of the parts and, more specifically, the invention relates toa seal for a rotatable shaft.

2. Related Prior Art

Seals are used in a variety of applications to provide a fluid-tightconnection between two parts, such as a rotating shaft and a relativelystationary housing. A first portion of the seal usually encircles therotating shaft and a second portion is mounted to the housing. The firstportion includes a rotating face that cooperates with a non-rotatingface associated with the second portion.

It has been observed that providing a fully floating mechanical shaftseal free of clamping distortions and free to align itselfperpendicularly to the shaft is desirable. U.S. Pat. No. 3,972,536discloses a rotating shaft seal assembly including a first ring portionaffixed to a shaft with set screws. The rotating shaft seal assemblyalso includes a second ring portion affixed to a housing and a sealprovided between the second ring portion and the first ring portion.

SUMMARY OF THE INVENTION

The present invention provides a seal assembly for relatively moveableparts having an inner case operable to encircle a rotatable shaft. Thecase includes a body and first and second flanges extending radiallyoutward from the body. The assembly also includes first and secondsealing discs encircling the inner case between the first and secondflanges. The discs provide respective surfaces that sealingly engage thefirst and second flanges. A spring also encircles the inner case betweenthe first and second sealing discs and urges the first and secondsealing discs against the first and second flanges. In a presentlypreferred embodiment of the invention, the spring is a wave spring.

The seal assembly according to the present invention can maintain a sealin an environment where a fluid pressure drop can occur. The springexerts a relatively constant axial force on the sealing disc against theflanges of the inner case. Also, the sealing discs include innerapertures that are sized to permit transverse movement of the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention willbecome more readily appreciated when considered in connection with thefollowing detailed description and appended drawings, wherein:

FIG. 1 is a perspective, partial cross-section view of a seal assemblyaccording to the exemplary embodiment of the invention; and

FIG. 2 is a cross-sectional view of the exemplary embodiment of the sealassembly shown in FIG. 1 in an operating environment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 1 and 2, the present invention provides a sealassembly 10 for providing a seal between relatively moveable parts, suchas a housing 12 and a shaft 14. The shaft 14 is rotatable about an axis16 relative to the housing 12. The housing 12 and shaft 14 can beassembled to a vehicle. In alternative embodiments of the invention, theseal can be disposed in any environment having a rotating shaft and astationary structure.

The assembly 10 includes an inner case 18 disposable in axially androtatably fixed relation about the rotatable shaft 14 for rotationtherewith. The inner case 18 rotates in response to rotation of theshaft 14 about the axis 16. The inner case 18 includes a body 20 andfirst and second flanges 22, 24 extending from opposite ends 26, 28 ofthe body 20. A length of the body 20 is defined between the first andsecond ends 26, 28. The body 20 includes an inner surface 30 facing theshaft 14 and an outer surface 32 facing away from the shaft 14. Thefirst and second flanges 22, 24 extend radially outward with respect tothe axis 16 from the outer surface 32 of the body 20. The first andsecond flanges 22, 24 define inwardly facing sealing surfaces 34, 36,respectively.

The seal assembly 10 also includes first and second sealing discs 38, 40that encircle the body 20 adjacent the first and second flanges 22, 24.The sealing discs 38, 40 extend substantially perpendicular to the axis16. The discs 38, 40 define surfaces 42, 44, respectively, thatsealingly engage the surfaces 34, 36, respectively. In alternativeembodiments of the invention, the sealing discs 38, 40 could befrusto-conical or any desired shape between the sealing surfaces 34, 36and the outer case 46. It is preferred that the discs 38, 40 bedisc-shaped for sealing engagement with the sealing surfaces 34, 36.

The sealing discs 38, 40 are substantially fixed to the housing 12. Forexample, the flanges 22, 24 move relative to the discs 38, 40 when theshaft 14 is rotating. In the exemplary embodiment of the invention, thediscs 38, 40 are fixedly associated with an outer case 46 which ismounted to the housing 12. The outer case includes first and secondflanges 48, 50. The discs 38, 40 are pressed against the flanges 48, 50with a spacer element 52.

The assembly 10 also includes a spring 54 for constantly urging thefirst and second sealing discs 38, 40 against the first and secondflanges 22, 24, respectively. The spring 54 encircles the body 20between the first and second sealing discs 38, 40. In a presentlypreferred embodiment of the invention, the spring 54 is a wave spring.The spring rate of the spring 54 is controlled to control the sealingforce between the surfaces 34, 42 and the surfaces 36, 44. The rate ofwear of the assembly can be controlled by controlling the sealing force.For example, the greater the spring force, the greater the sealing forceand the shorter the life of the assembly.

The spacer element 52 cooperates with the spring 54 such that theradially outermost ends of the discs 38, 40 are substantially fixedrelative to one another whereas the radially innermost ends of the discs38, 40 are moveable relative to one another. As a result, the portion ofthe seal assembly 10 closest to the moving shaft 14 is relatively morerobust while the portion of the seal assembly 10 furthest to the movingshaft 14 is relatively more rigid. The portion of the seal assembly 10closest to the moving shaft 14 can accommodate slight movement of theshaft 14 along the axis 16. The spacer element 52 can be integral withthe outer case 46.

Also, the rate of turning torque required to overcome frictional forcebetween the discs 38, 40 and the flanges 22, 24 can be controlled bycontrolling the spring rate of the spring 54. For example, the greaterthe spring rate, the greater the turning torque required to overcomefriction forces. In a presently preferred embodiment of the invention,the assembly 10 includes first and second washers 56, 58, to enhanceengagement of the spring 54 with the first and second sealing discs 38,40. The washer 56 is positioned between the spring 54 and the sealingdisc 38. The washer 56 is positioned between the spring 54 and thesealing disc 40.

The spring 54 enhances the robustness of the seal between the sealingdiscs 38, 40 and the flanges 22, 24. For example, in an operatingenvironment where the fluid sealed off by the assembly 10 is subjectedto pressure drops, the spring 54 can compensate for pressure drops byproviding a relatively constant sealing force. The spring 54 actsconcurrently on the sealing cooperation between the surfaces 34, 42 andbetween the surfaces 36, 44.

The first and second sealing discs 38, 40 define apertures 60, 62 facingthe outer surface 32 of the body 20. The aperture 60, 62 are sizedlarger than the outside diameter of the outer surface 32 and a gap isdefined between the apertures 60, 62 and the outer surface 32. The gapaccommodates movement of the shaft 14 transverse to the axis 16.

The radial or transverse overlap between the flanges 22, 24 with respectto the sealing discs 38, 40 is determined in view of the extent oftransverse movement of the shaft 14. For example, the flange 22 and thefirst sealing disc 38 radially overlap between the aperture 60 and asurface 64 defined by the flange 22. The extent of this radial overlapis selected such that when the shaft 14 is offset from the axis 16 amaximum possible distance, the radial distance between the aperture 60and the surface 64 is sufficient to seal the surface 34 with the surface42.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the invention may be practicedotherwise than as specifically described. The invention is defined bythe claims.

1. A seal assembly for providing a seal between relatively moveableparts comprising: an inner case operable to fixedly encircle a rotatableshaft and having a body defining length and first and second flangesextending from opposite ends of said body; first and second sealingdiscs encircling said body and respectively disposed adjacent said firstand second flanges; and a spring encircling said body and urging saidfirst and second sealing discs against said first and second flangesrespectively.
 2. The seal assembly of claim 1 wherein said inner case isrotatable relative to said first and second sealing discs.
 3. The sealassembly of claim 1 wherein said spring is further defined as a wavespring.
 4. The seal assembly of claim 3 further comprising: first andsecond washers respectively disposed on opposite sides of said wavespring wherein said first washer being disposed between said wave springand said first sealing disc and said second washer being disposedbetween said wave spring and said second sealing disc.
 5. The sealassembly of claim 1 further comprising: an outer case encircling saidfirst and second sealing discs and having a second body and third andfourth flanges extending from opposite ends of said second body, whereinsaid first sealing disc being adjacent said third flange and said secondsealing disc being adjacent said fourth flange.
 6. The seal assembly ofclaim 5 further comprising: a spacer element disposed between said firstand second sealing discs and between said third and fourth flanges tomaintain said first sealing disc and said third flange in contact withone another to maintain said second sealing disc and said fourth flangein contact with one another.
 7. The seal assembly of claim 1 whereinsaid first and second sealing discs respectively include first andsecond apertures radially spaced from said body.